Download 22.1 Characteristics of the Atmosphere

22.1 Characteristics of the Atmosphere
Characteristics of
the Atmosphere
Section 22.1
Atmosphere
· layer of gases that surrounds the Earth
· air = mixture of chemical elements and compounds
in the atmosphere
· functions (2)
protect Earth's surface from the sun's radiation
help regulate Earth's surface temperature
· gases
Composition of Atmosphere
nitrogen - 78%, oxygen - 21%, argon, CO2, and other - 1%
· water vapor
enters by evaporation from
oceans, fresh water, and plants
most near surface
decreases with height
· ozone - O3
form of oxygen gas
absorbs harmful ultraviolet radiation from the sun
less ozone = more UV rays reach Earth's surface = sunburn
and cancer
thinning results from chlorofluorocarbons (CFCs) which
breaks down ozone
· particulates
Atmospheric Pressure
· pressure exerted on Earth's surface
by the atmosphere
· decreases as altitude increases
gravity not as strong at high
altitude, so air molecules move
further apart and exert less pressure
· decreases as temperature increases
molecules move further apart as air
heats up
· decreases as water vapor increases
water vapor is less dense (or lighter) than oxygen
and nitrogen molecules
dust, ash, pollen, bacteria, salt
helps form fog & rain (water clings to particulates)
tiny particles can stay in the air for months or years
Measuring Atmospheric Pressure
· tool = barometer
· units = atmosphere (atm),
millimeters of mercury (mm Hg),
and millibars (mb)
· standard atmospheric pressure at
sea level = 1 atm = 760 mm Hg =
1000 mb
Layers of Atmosphere
· 4 layers based on temperature
· troposphere = 0 - 12 km
· stratosphere = 12 - 50 km
contains ozone layer
· mesosphere = 50 - 80 km
· thermosphere
ionosphere = 80 - 400 km
exosphere = 400 - ? km
22.1 Characteristics of the Atmosphere
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Troposphere
closest to Earth's surface
weather occurs here
contains gases essential to life
temperature decreases with altitude
heated by thermal energy that comes from Earth's
surface
· average altitude = 12 km
depends on latitude and season
Thermosphere
· temperature increases with altitude
nitrogen and oxygen absorb solar energy
as high as 1000 C
· ionosphere = lower portion
ions formed when UV rays from sun knock electrons
off oxygen atoms
· exosphere = upper limit of indefinite altitude
Stratosphere & Mesosphere
STRATOSPHERE
· strong winds and few
weather changes
· contains ozone
· temperature
increases with
altitude
heated by absorption
of solar energy by
ozone
MESOSPHERE
· temperature decreases
with altitude
· coldest temperatures in
atmosphere